Apart from preparation, which is often 80% of the job, painting an exterior wall is about as easy as it gets. But there are still a few guidelines useful to follow to achieve the best final result.
Proper paint selection is first and foremost. In most cases, an oil-based or alkyd paint is the best choice. It creates a long-lasting surface that resists weathering. On the other hand, latex breathes. So, in houses where moisture is likely to get trapped it can be preferable.
Deciding on whether a primer is needed can be difficult. If the surface would absorb too readily, making it necessary to use several top coats, go with primer. It's much less expensive and creates a good bond for the final painting, which may be done in a single coat. It's also vital when painting a different color, since it will help prevent color bleed through.
After masking is completed, you're ready to go. Just keep the following tips in mind to prevent unsightly errors.
Rapid peeling results from a combination of factors. Painting over wood that contains too much moisture is the most common. Since preparation involves washing the surface first, it's important to ensure that the wood is well dried before starting. A moisture meter can be used to determine the moisture content.
Moisture can penetrate wood after the paint job, too, though. Latex breathes and allows trapped moisture to evaporate off the surface. But it won't generally weather as well, so there's a trade off. Decide based on your individual circumstances. In areas or houses where rain is scarce or water unlikely to get inside, it's not usually a problem.
Normal peeling from age and weathering is a different animal. That can result from using latex. It may also be from painting a poor surface, such as grayed wood. The fibers are tight and the wood cells have changed so they no longer absorb paint as readily. Good preparation is the key to preventing this problem, or at least slowing it down. A good oxalic acid wash may be just the thing.
A surface flaw called alligatoring is another common problem. As the paint dries, it gathers together, exposing the undercoat. That will happen if the topcoat doesn't adhere well to the surface below. Good sanding and/or primer is the key to preventing it.
Wrinkling has a similar look, but occurs when paint droops like sagging skin. That can happen when the consistency of the paint used is too thick. Oil-based paints are especially prone to this. They are thicker to begin with and are often not thinned properly before beginning. They also dry more slowly. If another coat is applied before the first one is fully dry, wrinkling may result.
Sagging looks similar, but here the error is incorrect brushing technique. Too much paint on the brush at one time can produce too thick a coat. Spreading it out only does so much. Simply wipe the brush over the rim before applying. Don't try to rush the job by getting as much paint as possible into the brush.
Blisters, by contrast, have an altogether different appearance. Just like the skin condition, paint blisters are small, oval bumps on the surface.
They may be due to moisture, in which case better preparation was needed. But they can also occur as the result of solvent getting trapped underneath the coat. If wood appears underneath the blister, moisture was the likely cause. If paint appears, solvent is probably the culprit.
In the first case, ensure the surface is dry before painting. Solvent blisters can occur when painting in too-high temperatures. The high heat causes the paint compounds to separate and the solvent gets trapped in a bubble.
With proper preparation and technique your exterior walls can get painted quickly and with a stellar result. A little thought and effort before hand, and a little patience during, will produce a great looking exterior wall.